Supervision, Health and Safety, and Contracting Practice
Supervision
Licensed certifying drainlayers carry responsibility for the work they supervise as well as the work they do. Trainees and limited certificate holders must work under the supervision arrangement and to the standard the Board requires - supervision must be real, with the supervisor able to check and correct the work, and with the trainee's competence matched to the task. Verify work before it is covered, sign off only what you have inspected, and record who did what.
Health and safety
The Health and Safety at Work Act 2015 imposes duties on every PCBU and officer: eliminate or minimise risk so far as reasonably practicable, engage with workers, provide information, training and supervision. On a drainage site the big hazards are excavations (collapse, falls, falling objects, services, water), confined spaces, service strikes, traffic, plant movement, manual handling, chemicals and silica or asbestos in older ground. Practical controls include a site-specific safety plan, hazard board, daily briefings, shoring or benching, edge protection, ladders, spoil set back from the trench edge, gas testing and permits for confined spaces, service location before digging, and a traffic management plan. Notifiable events must be reported.
Contracting
Understand your contract: quote versus estimate, payment claims and payment schedules under the Construction Contracts Act 2002 (with its strict timeframes and adjudication route), retentions held in trust, variations in writing, and standard forms such as NZS 3910. Consumer Guarantees Act and Fair Trading Act obligations apply to residential clients. Insurance, guarantees and warranty terms should be agreed before work starts.
Traps
Treating supervision as a signature. Entering an unsupported trench because "it's only shallow". Verbal variations with no record. Missing a payment claim deadline.
Rule of thumb: no person in a trench deeper than 1.5 m unless it is properly shored, benched or otherwise made safe - and never rely on "it looks firm".